transient transport error report for LLD timeout

@@ -28,12 +28,43 @@
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include <linux/writeback.h>
+#include <linux/sysctl.h>
 
 /*
  * for max sense size
  */
 #include <scsi/scsi_cmnd.h>
 
+/* for transient error response */
+unsigned int request_timeout;
+
+static ctl_table req_table[] = {
+  { .ctl_name = BLOCK_REQUEST_TIMEOUT,
+    .procname = "req_timeout",
+    .data = &request_timeout,
+    .maxlen = sizeof(request_timeout),
+    .mode = 0644,
+    .proc_handler = &proc_dointvec },
+  { }
+};
+
+static ctl_table blk_root_table[] = {
+  { .ctl_name     = CTL_BLK,
+    .procname     = "block",
+    .mode         = 0555,
+    .child        = req_table },
+  { }
+};
+
+int __init blk_init_sysctl(void);
+
+static struct ctl_table_header *blk_table_header;
+
+module_param(request_timeout, int, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(request_timeout, "Set timeout value for request");
+
+static void request_timer_expired(unsigned long data);
+
 static void blk_unplug_work(void *data);
 static void blk_unplug_timeout(unsigned long data);
 

@@ -2158,6 +2189,11 @@
 	req->q = NULL;
 	req->rl = NULL;
 
+	/* delete timer for transient error */
+	if ((req->flags & REQ_SET_TIMER) && !(req->flags & REQ_TE_RESPONSE)) {
+		del_timer(&req->te_timeout);
+	}
+
 	/*
 	 * Request may not have originated from ll_rw_blk. if not,
 	 * it didn't come out of our reserved rq pools

@@ -2465,6 +2501,17 @@
 	req->rq_disk = bio->bi_bdev->bd_disk;
 	req->start_time = jiffies;
 
+	/* timer set for transient error */
+	/* req->flags |= REQ_FAILFAST; for transient error test */
+	if (blk_noretry_request(req) && unlikely(request_timeout)) {
+		req->flags |= REQ_SET_TIMER;
+		init_timer(&req->te_timeout);
+		req->te_timeout.data = (unsigned long)req;
+		req->te_timeout.expires = jiffies + request_timeout*HZ;
+		req->te_timeout.function = request_timer_expired;
+		add_timer(&req->te_timeout);
+	}
+
 	add_request(q, req);
 out:
 	if (freereq)

@@ -2787,6 +2834,11 @@
 	int total_bytes, bio_nbytes, error, next_idx = 0;
 	struct bio *bio;
 
+	if ((req->flags & REQ_SET_TIMER) && (req->flags & REQ_TE_RESPONSE)) {
+		printk("already set TE_RESPONSE\n");
+		return 0;
+	}
+
 	/*
 	 * extend uptodate bool to allow < 0 value to be direct io error
 	 */

@@ -3035,6 +3087,17 @@
 
 	blk_max_low_pfn = max_low_pfn;
 	blk_max_pfn = max_pfn;
+
+	blk_init_sysctl();
+
+	return 0;
+}
+
+int __init blk_init_sysctl(void)
+{
+	blk_table_header = register_sysctl_table(blk_root_table, 1);
+	if (!blk_table_header)
+		return -ENOMEM;
 	return 0;
 }
 

@@ -3310,3 +3373,19 @@
 		kobject_put(&disk->kobj);
 	}
 }
+
+static void
+request_timer_expired(unsigned long data)
+{
+	struct request *req = (struct request *)data;
+
+	printk("request_timer_expired()!\n");
+
+	while (end_that_request_first(req, 0, req->nr_sectors))
+		;
+	req->ref_count++;
+	req->flags |= REQ_TE_RESPONSE;
+	end_that_request_last(req);
+
+	return;
+}

diff -uarN linux-2.6.9-rc2/include/linux/blkdev.h linux-2.6.9-rc2te/include/linux/blkdev.h
@@ -163,6 +163,9 @@
 	 * For Power Management requests
 	 */
 	struct request_pm_state *pm;
+
+	/* Used to time out for transient error response */
+	struct timer_list te_timeout;
 };
 
 /*

@@ -197,6 +200,8 @@
 	__REQ_PM_SHUTDOWN,	/* shutdown request */
 	__REQ_BAR_PREFLUSH,	/* barrier pre-flush done */
 	__REQ_BAR_POSTFLUSH,	/* barrier post-flush */
+	__REQ_TE_RESPONSE,      /* return transient error response  */
+	__REQ_SET_TIMER,        /* set timer for transient error response */
 	__REQ_NR_BITS,		/* stops here */
 };
 

@@ -224,6 +229,8 @@
 #define REQ_PM_SHUTDOWN	(1 << __REQ_PM_SHUTDOWN)
 #define REQ_BAR_PREFLUSH	(1 << __REQ_BAR_PREFLUSH)
 #define REQ_BAR_POSTFLUSH	(1 << __REQ_BAR_POSTFLUSH)
+#define REQ_TE_RESPONSE	(1 << __REQ_TE_RESPONSE)
+#define REQ_SET_TIMER	(1 << __REQ_SET_TIMER)
 
 /*
  * State information carried for REQ_PM_SUSPEND and REQ_PM_RESUME

diff -uarN linux-2.6.9-rc2/include/linux/sysctl.h linux-2.6.9-rc2te/include/linux/sysctl.h
@@ -61,7 +61,8 @@
 	CTL_DEV=7,		/* Devices */
 	CTL_BUS=8,		/* Busses */
 	CTL_ABI=9,		/* Binary emulation */
-	CTL_CPU=10		/* CPU stuff (speed scaling, etc) */
+	CTL_CPU=10,		/* CPU stuff (speed scaling, etc) */
+	CTL_BLK=11		/* Block */
 };
 
 /* CTL_BUS names: */

@@ -764,6 +765,11 @@
 	ABI_FAKE_UTSNAME=6,	/* fake target utsname information */
 };
 
+/* /proc/sys/block */
+enum {
+	BLOCK_REQUEST_TIMEOUT=1,
+};
+
 #ifdef __KERNEL__
 
 extern void sysctl_init(void);